lwip---DHCP

DHCP流程

 

 关于DHCP服务器的offerack阶段是单播还是广播的研究

看来都可以,DHCP协议有一位是表示发的是单波还是广播。

可以广播包,也可以单波包,因为第一步服务器肯定知道了客户端MAC,知道MAC就可以只发个单波就可以(交换机MAC-端口表,这样就可以单波传送特定端口了)

 

 LwIP DHCP流程:
1: netif_add: dhcpif  设为全0
 netif_set_default
 netif_set_up

2: dhcp_start

3: dhcpif->ip_addr.addr 该值不为0则说明取得到IP
       此时需要保存IP, Mask, GateWay, 否则在以下部操作之后就没了
 dhcp_release   释放DHCP, 该操作后不需要调用netif_set_down
 dhcp_stop    remove the DHCP client.

4: netif_set_addr   用DHCP得到的值重设IP, Mask, GateWay.

5: netif_set_up   必须设置!

注: dhcp_fine_tmr();  必须调用
 dhcp_coarse_tmr();  要求调用
 

 

  IP4_ADDR(&ipaddr, 0, 0, 0, 0); // IP地址
  IP4_ADDR(&netmask, 0, 0, 0, 0); // 子网掩码
  IP4_ADDR(&gw, 0, 0, 0, 0);  // 网关
 

  netif_add(&ethif, &ipaddr, &netmask, &gw,
  NULL, ethernetif_init, ip_input); // 建立LwIP网络界面
  netif_set_default(&ethif);    // 设为默认网络界面
  netif_set_up(&ethif);     // 启动网络界面

  ip_init();        // 初始化IP模块
  tcp_init();        // 初始化TCP模块

  result = dhcp_start(&ethif);

 

 while(1)
 {  
  ethbuf_len = ENET_HandleRxPkt(ethbuf);
           // 接收来自NIC的数据包
  if(ethbuf_len > 0)     // 有数据包被接收?
   ethernetif_input(&ethif);  // 是,将数据包交给LwIP处理

  
   if(ethif.dhcp!=NULL &&
      ethif.dhcp->offered_ip_addr.addr!=0 &&
      ethif.dhcp->offered_sn_mask.addr!=0 &&
   ethif.dhcp->offered_gw_addr.addr!=0)
   {
  
     netif_set_addr(&ethif, &(ethif.dhcp->offered_ip_addr)
                    ,&(ethif.dhcp->offered_sn_mask)
        , &(ethif.dhcp->offered_gw_addr));
    
      netif_set_default(&ethif);    
      netif_set_up(&ethif);     

       ip_init();             

      dhcp_stop(&ethif);
   }

 }
 
}

 

 

dhcp结构体

struct dhcp
{
  /** current DHCP state machine state */
  u8_t state;
  /** retries of current request */
  u8_t tries;
  /** transaction identifier of last sent request */
  u32_t xid;
  /** our connection to the DHCP server */
  struct udp_pcb *pcb;
  /** (first) pbuf of incoming msg */
  struct pbuf *p;
  /** incoming msg */
  struct dhcp_msg *msg_in;
  /** incoming msg options */
  struct dhcp_msg *options_in;
  /** ingoing msg options length */
  u16_t options_in_len;

  struct pbuf *p_out; /* pbuf of outcoming msg */
  struct dhcp_msg *msg_out; /* outgoing msg */
  u16_t options_out_len; /* outgoing msg options length */
  u16_t request_timeout; /* #ticks with period DHCP_FINE_TIMER_SECS for request timeout */
  u16_t t1_timeout;  /* #ticks with period DHCP_COARSE_TIMER_SECS for renewal time */
  u16_t t2_timeout;  /* #ticks with period DHCP_COARSE_TIMER_SECS for rebind time */
  struct ip_addr server_ip_addr; /* dhcp server address that offered this lease */
  struct ip_addr offered_ip_addr;
  struct ip_addr offered_sn_mask;
  struct ip_addr offered_gw_addr;
  struct ip_addr offered_bc_addr;
#define DHCP_MAX_DNS 2
  u32_t dns_count; /* actual number of DNS servers obtained */
  struct ip_addr offered_dns_addr[DHCP_MAX_DNS]; /* DNS server addresses */
 
  u32_t offered_t0_lease; /* lease period (in seconds) */
  u32_t offered_t1_renew; /* recommended renew time (usually 50% of lease period) */
  u32_t offered_t2_rebind; /* recommended rebind time (usually 66% of lease period)  */
#if LWIP_DHCP_AUTOIP_COOP
  u8_t autoip_coop_state;
#endif
/** Patch #1308
 *  TODO: See dhcp.c "TODO"s
 */
#if 0
  struct ip_addr offered_si_addr;
  u8_t *boot_file_name;
#endif
};

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